In December of 2015, I had 985 hours on my Yanmar 370HP and brought it to a very reputable (Yanmar authorized) marina (Haven Harbour) in MD. I've attached the completed work order below. Cost about $3300. I didn't see anything in there about the heat exchangers and was told they ran Rydlyme through the system. I wasn't thrilled with the answer, but who am I to challenge an authorized dealer?

Fast forward to December of 2016 (that is NOW, in case you are not paying attention)... I have moved to VA and have had a highly recommended local mechanic replace my mixing elbow (which the previous mechanic had pointed out was in need of replacing). So the new mechanic says that it doesn't look like the heat exchangers have been touched. I explained what was done last year. He tells me they should really be removed, cleaned, inspected, etc. His estimate for $3400 is below. Yikes. Thoughts??

Greetings,
So the new mechanic says that it doesn't look like the heat exchangers have been touched. I explained what was done last year. He tells me they should really be removed, cleaned, inspected, etc. His estimate for $3400 is below. Yikes. Thoughts??

Sounds like you finally have a smart mechanic. Yanmar metallurgy on HXers is tricky thus leading to the better guys saying take them off. Now having said that, I'm sure several will chime in and say how happy they are with product XYZ that will rinse away your worries..

To make your life simpler in this regard, hook up a simple fresh water flush which will largely ameliorate the need to frequently clean the HXers. After coolers are a different story. They have to come off every few years and be cleaned, pressure tested and re-assembled by the book.

I hope you will me allow me to jump on the thread with you, with a similar dilemma.

We have a Volvo Penta D4-260 with about 400 hours on it. The engine was placed in-service in 2006, and we purchased IRENE 2 years ago at the 80-hour mark. We are particular about maintenance, being a single-engine boat and operating all year in some remote areas. Fortunately we have found a service outfit we trust.

Our manual says to clean/inspect the charge air cooler and heat exchanger/oil cooler every 1200 hours or 5 years. Out trusted service outfit tells us they recommend to WAIT on that until there is an indication of a problem, as once the respective coolers are reassembled they will require servicing much more frequently.

Over on boatdiesel, and also on ybw, there are varying opinions, of course. My next move, in the next week or so, is to call 2 other reputable VP shops to learn their advice. For us, the coolers are the only maintenance item on the boat that remains unaddressed.

In the meantime, I recommend boatdiesel as a source of information. It's heavy on content and light on nonsense - well worth the annual price.

I should also note that I didn't see any change in engine temp after having the "rinse" on the first go round. I realize that temp gauges may not be accurate, but I run right around 185 deg, which seems a bit hot.

Jeff - regarding the fresh water flush... I've got a Y valve in my bilge where I can either direct seawater into the strainer OR to a hose with a strainer that is very accessible. I'm told this is known as a "crash pump" so that if you are taking on water that you could use the engine to assist in pumping it out? I'd imagine I could very easily slip a 5 gallon bucket on that and run fresh water after each use. Sounds like a good idea, right?

I have done most of the work outlined above myself on my Yanmar, so from that basis here are some observations:

The first mechanic erred by not removing, disassembling, cleaning, greasing, reassembling and pressure testing the air cooler. Acid wash will remove scale, but it will not protect the air/water side sealing surfaces which deteriorate over time and cannot clean the air side.

Also the use of synthetic oil in the main and genset engine is a total waste of money.

I can't fault the second mechanic's plan. He proposes removing all of the heat exchangers to clean them and that is the first class way to do it. I happen to believe that acid flushing every 3-5 years will do almost as good, but only if a complete service is first done on the air cooler, particularly pressure testing.

I believe that removing injectors for testing on a good running engne at 1,000 hours is overkill, but I understand that is what Yanmar recommends.

IRENE: Waiting to notice a problem with the air cooler is like waiting for your engine to breakfast on sea water. It could be a very expensive wait. The comment that once you open the air cooler, it will require more frequent servicing is total BS. If you service them right, slather them with waterproof grease before reassembling, then they will last much longer than new from the factory with no grease.

sunchaser: A fresh water flush will help limit metal corrosion and zinc wastage in between runnings. It might also help prevent some dark loving critters from living and dying on the tubes between runnings. But I don't think it does much for scale formation. Scale forms when engine heat precipitates calcium, magnesium and other compounds in sea water on the heat exchanger tubes and that will happen whether you flush or not.

Jeff - regarding the fresh water flush... I've got a Y valve in my bilge where I can either direct seawater into the strainer OR to a hose with a strainer that is very accessible. I'm told this is known as a "crash pump" so that if you are taking on water that you could use the engine to assist in pumping it out? I'd imagine I could very easily slip a 5 gallon bucket on that and run fresh water after each use. Sounds like a good idea, right?

Jack:

I also have those fittings on the sea water system on my Pilot 34. But the hose to the bilge is very inaccessible for use as a fresh water flush. The picture below shows what I did and it is very easy to use.

Jeff - regarding the fresh water flush... I've got a Y valve in my bilge where I can either direct seawater into the strainer OR to a hose with a strainer that is very accessible. I'm told this is known as a "crash pump" so that if you are taking on water that you could use the engine to assist in pumping it out? I'd imagine I could very easily slip a 5 gallon bucket on that and run fresh water after each use. Sounds like a good idea, right?

Jack,

Yes! I would recommend it. We store IRENE on the trailer and she gets a fresh water flush after each use. You could even drop a bit of Salt Away in your "flush bucket". Unfortunately we don't have a similar setup for when she is in the water, which is a couple of weeks for vacation, and many weekends.

It was easy to do. I removed the lid, clamped it in a vise and drilled and tapped a hole for the street elbow you see in the pic. I considered silver soldering the joint but just tightening up the fitting seemed good enough.